The goal of this project is to develop a new microarray system for performing gene expression analysis directly with total RNA without labeling and reverse transcription to cDNA. Achieving this goal will provide a critical breakthrough and establish a new standard in microarray field. Indeed, although microarray technique has been widely studied and proved to be successful in many applications, there are still many challenges in this field. First, the traditional microarray detection requires the total RNA to be reverse transcribed and labeled with reporter molecules, which is costly and time-consuming. Second, the PCR amplification of target sequences may give rise to systematic errors and biased hybridization signals. Third, the cost for a microarray instrumentation is high. Reducing the cost of instrumentation and day-by-day operation will make microarray technology more accessible to small research institutions and clinics. The key innovation of this project is a new RNA detection technique which employs electrostatic interaction of the target molecules and nanometer-size particles. This detection technique allows to use total RNA directly for hybridization experiment without reporter incorporation and reverse transcription from RNA to cDNA. The technique also allows inexpensive instrumentation to be used for highly-sensitive detection of DNA and RNA in gene expression analysis. With the recent reports of using microarrays in clinical tests for tumorogenesis and prognosis of a chemotherapy outcome (Science, 303:1754), introducing an advanced and inexpensive microarray platform will find fast adoption in more than 500 clinical laboratories and hundreds of life science research laboratories in US alone. [unreadable] [unreadable]